Aged soils contribute little to contemporary carbon cycling downstream of thawing permafrost peatlands. ...

• Main Authors: Tanentzap, Andrew J, Burd, Katheryn, Kuhn, McKenzie, Estop-Aragonés, Cristian, Tank, Suzanne E, Olefeldt, David
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: boreal; carbon cycling; disturbance; food webs; permafrost peatlands; streams; terrestrial-aquatic linkages; Carbon; Carbon Cycle; Ecosystem; Permafrost; Soil; Canada; permafrost; Subarctic; Thermokarst
• Online Access: https://dx.doi.org/10.17863/cam.71218; https://www.repository.cam.ac.uk/handle/1810/323760

Vast stores of millennial-aged soil carbon (MSC) in permafrost peatlands risk leaching into the contemporary carbon cycle after thaw caused by climate warming or increased wildfire activity. Here we tracked the export and downstream fate of MSC from two peatland-dominated catchments in subarctic Canada, one of which was recently affected by wildfire. We tested whether thermokarst bog expansion and deepening of seasonally thawed soils due to wildfire increased the contributions of MSC to downstream waters. Despite being available for lateral transport, MSC accounted for ≤6% of dissolved organic carbon (DOC) pools at catchment outlets. Assimilation of MSC into the aquatic food web could not explain its absence at the outlets. Using δ13 C-Δ14 C-δ15 N-δ2 H measurements, we estimated only 7% of consumer biomass came from MSC by direct assimilation and algal recycling of heterotrophic respiration. Recent wildfire that caused seasonally thawed soils to reach twice as deep in one catchment did not change these ...